1. Field of the Invention
The invention relates to an arrangement for measuring transfer impedances of coaxial systems, comprising a generator, which is connected via a coaxial, supplying system to a conductor shield of the coaxial system at a first end of the coaxial system, and a voltage measuring instrument, which is connected at the first end between the conductor shield and the inner conductor of the coaxial system.
2. Discussion of Background
With reference to the design of systems which do justice to the requirements of electromagnetic compatibility (EMC) it is important to be able to forecast the coupling behavior of transient, non-sinusoidal signals in electrical conductors, especially in shielded coaxial cables. Apart from the amplitude, the phase of the transfer impedance must also be known. The Standard IEC-96-1A indicates a method to be used in measuring the amplitude of the transfer impedance in the frequency range. However, the directions for carrying out the method are capable of being properly effected only for frequencies which are not too high (up to approximately 30 MHz). Accordingly, to date measurements have been limited to this frequency range, in the main.
With this Standard, a problem is represented by the required soldered connection between the supplying system and the cable shield. In practice, it is found that it is difficult to create a good soldered connection, without damaging the cable dielectric, or altering the conductor shield (an attrition of tin-lead solder through the braided screen). A further problem is represented by the required matched cable head. Firstly, resistors are frequency-dependent, i.e. the matching occurs only in a definite frequency range), and secondly, during assembly there is often a gap between the resistor and the cable, which leads to an inhomogeneous cable section. This is especially to be avoided for the higher frequency range, since the correction formula given by the upper Standard presupposes a homogeneous cable section. For the same reason, it is also important that the cable runs coaxially, which, however, cannot be observed without difficulty for the Standard IEC-96-1A.
All the described disadvantages of the prior art entail that measurements have mainly been restricted to a frequency range in which the cable can be considered small as compared with the wavelength.